Menopause, a normal part of the aging process, is the period during which the level of estrogen and progesterone secreted by the ovaries gradually declines. Approximately 80% of women experience mild or few symptoms. However some women have severe symptoms including: hot flushes, heavy sweating, anxiety, panic, or depression, drying and wrinkling of the skin, vaginal dryness and discomfort, urinary stress incontinence, cystitis, insomnia, irritability and osteoporosis. A report published by the World Health Organization in 1990 estimated that the total population of postmenopausal women in the world was 476 million. By 2030, the predicted population will reach 1.2 billion.
The current treatment to relieve menopausal syndrome is hormone replacement therapy (HRT), which consists of administration of supplementary exogenous estrogen or estrogen plus progestin most frequently using pills, implants under the skin or skin patches. While HRT increases the circulating estrogen level by providing exogenous estrogen to menopausal women, the appropriate dosage and the duration of treatment are difficult to determine due to individual variations in physiological conditions among menopausal women. Consequently, HRT is sometimes ineffective and prone to causing side effects including endometrioma, breast and ovarian cancer, coronary heart disease and stroke.
Osteoporosis results from an increased rate of bone resorption and relatively decreased rate of bone formation, resulting in reduced bone mass and micro-architectural deterioration of the skeleton, and an increased risk of fractures. Bone remodeling increases substantially in the years after menopause and remains elevated in older osteoporosis patients indicating that the loss of ovarian hormones during menopause is one of the major risk factors for osteoporosis. Bone status as such contributes to the increases in age-related skeletal fragility in women. It has been shown that trabecular bone mineral density, trabecular bone volume fraction, trabecular thickness and trabecular number all decrease with age. Also, a lower bone mass is primarily characterized by a smaller plate-to-rod ratio. All these changes weaken bone strength and increase the risk of osteoporotic fracture.
Weight-bearing exercises have an osteogenic effect in postmenopausal women. However, vigorous exercises are needed to engender an osteogenic effect in the elderly. Use of HRT in combination with weight bearing exercises has been shown to have a synergistic effect. This shows that the osteogenic response may be enhanced by the administrated estrogen.
Selective estrogen receptor modulator (SERM) is a remedy in particular for relieving postmenopausal osteoporosis. However, there is no evidence showing that SERM would increase the endogenous estrogen level in menopausal women, and therefore, may not relieve menopausal syndromes other than osteoporosis.
Various studies have shown that proteins or other compounds isolated from different species of yam tuber have anti-oxidative, chitinase and immunomodulatory activities, including activating estrogen receptors. It is desirable to develop a cost-effective treatment for symptoms of menopausal syndrome in order to alleviate or prevent osteoporosis and/or cognitive decline resulting from low serum levels estrogen and progesterone levels.